Friction-Fusion Welding Of Strap
A variety of methods have been marketed and/or proposed over the years for securing together overlapping portions of a tensioned loop of thermoplastic strap encircling an article. One method is effected by first compressing the overlapping strap portions together and then creating a unidirectional or multidirectional bodily sliding frictional movement between the contacting surface regions of the overlapping strap portions to melt interface regions of the overlapping strap portions. The melted interface regions are allowed to solidify so as to bond the overlapping strap portions together.
This process, which can be generally described by the term friction-fusion welding, has proven to be especially effective with conventional thermoplastic strap materials such as nylon, polyester, polypropylene, and the like. Such conventional strap is typically provided in widths ranging from 5 mm. to 9.525 mm. and has a thickness ranging between about 0.254 mm and about 0.889 mm.
In conventional tools and machines for effecting a friction-fusion weld between overlapping portions of thermoplastic strap, an engaging member is provided for gripping the outwardly directed surface of one of the overlapping strap portions and an anvil is provided for contacting the outwardly directed surface of the other overlapping strap portion. The strap engaging surface of the engaging member and of the anvil may each be planar or may each be curved for receiving the overlapping strap portions. Relative movement is effected between the engaging member and the anvil so that at least some of the relative movement takes place in a planar or curved locus conforming to the planar or curved interface between the two overlapping strap portions.